Today Leetcode problem is rotating linked list . Doing it is a no brainer( Answer below). What I suddenly realize is you could pipe the boolean expression to simplify the boolean check later on. To jump straight on:

Was browsing through Medium coding problems of Leetcode( Oh yeah. I think Im at this level ) when I stumble upon this one — validating binary tree. Pfft. You dummy, NO WAY this is medium. Turns out it is harder than I thought ^^, not because it is hard but because of my stupid mistakes….